| Tea is one of the three largest non alcoholic beverages in the world. Tea processing is an important way to realize the conversion of economic value, and it is the main way to realize the transformation of fresh leaves into special agricultural products. In recent years, with the rapid development of China's tea industry, yellow tea consumption rises quietly, to guide and to adapt to the needs of the market, the yellow tea producing areas is committed to recovery, development and revitalization of the yellow tea industry. However, yellow tea industry will be faced with an urgent and realistic problem:one is in other teas are unusually fierce in competition, the yellow tea in the nationwide total low, influence is weak; second, traditional yellow tea is mainly oriented to manual, process is difficult to grasp, the yellow tea production efficiency is low, yield less, and the quality of the product has poor stability, different batches, different manufacturers, such as the production of product quality difference is bigger, urgent need for innovation in production and processing technology and study the mechanism of the production; the third, at present, yellow tea products market confusion, market sale yellow tea varying quality. Therefore, it is important to strengthen the research on the processing technology and quality of yellow tea, and to provide scientific data support for the development of yellow tea industry.The experimental basic processing technology and key technology was studied on the Sichuan famous yellow tea, roll shape and strip of yellow tea in this paper firstly, based on system analysis of the three modeling yellow tea processing quality formation, Based on three kinds of modeling yellow tea processing quality formation were systematically analyzed, the relevance between related to the process of biochemical composition changes with the sensory scores was theoreticalage quality changes were studied in Sichuan famous Yellow tea. Main research results are as follows:(l)The basic process and key technology of thrtea:fresh leaf?withering?roller de-enzyruing?heaping for yellowing?first firing?Shaping appearance(press bar)?full firing; curved yellow tea:fresh leaf?withering?roller de-enzyruing?heaping for yellowing?twising?first firing?full firing; bar yellow tea:fresh leaf?withering?roller de-enzyruing?heaping for yellow tea were studed, results showed that:optimal process, flat yellow for yellowing?twising?first firing?Shaping appearance?full firing. Parameters of processing tea were controlled, including: de-enzyruing time 1.5min, cast leaf speed to keep 1.5kg/min, lightde-enzyming (cylinder water removing machine pot in the middle temperature 210-220 ?), heaping for yellowing time 120min. Light twising 6min+Heavy twising 8min+Light twising 6min, first firing weight loss rate of 15%, Shaping appearance 15 min, finally 75 ? full firing, the obtained yellow tea appearance tight junction yellow, soup color was tender and Huang Mingliang, sweet aroma, refreshing tasted sweet alcohol, bottom of leaves yellow soft, the biochemical composition and ratio of appropriate, the quality was the best.(2) The systematic study was conducted on three yellow tea processing quality changes, the results showed that:There were extremely significant negative correlation between process sensory scores and tea polyphenols, catechins, caffeine and total chlorophyll in flat yellow tea. Correlation coefficients were -0.979?-0.986?-0.882 and-0.976, respectively. There were extremely significant positive correlation between process sensory scores and TFs, TRs, TBs and soluble sugar.The correlation coefficient respectively was 0.969?0.892,0.944 and 0.921. And water extract has a significant positive correlation, correlation coefficient was 0.839. The regression equation was established between the sensory scores and the chemical components Y=266.21-11.56X2-11.13X3-13.78X4+6.99X8-89.49X10, R2 was 0.9999. There were extremely significant negative correlation between process sensory scores and tea polyphenols, catechins, caffeine and total chlorophyll in Curl shaped yellow tea. Correlation coefficients respectively were-0.976?-0.946,-0.964 and -0.961. There were extremely significant positive correlation between process sensory scores and TFs, TRs, TBs, soluble sugar and water extract. The correlation coefficient respectively was 0.931, 0.969?0.959?0.908 and 0.946. And amino acid has a significant positive correlation, correlation coefficient was 0.839. The regression equation was established between the sensory scores and the chemical components Y=225.25-6.61X1+3.38X2+8.35X5-7.54X8, R2 was 0.9999. There were extremely significant negative correlation between process sensory scores and tea polyphenols, catechins, caffeine and total chlorophyll in bar yellow tea. Correlation coefficients respectively were -0.985,-0.993,-0.993 and -0.996 There were extremely significant positive correlation between process sensory scores and TFs, TRs, TBs, amino acid, soluble sugar and water extract. The correlation coefficient respectively was 0.991,0.984,0.972,0.862,0.975 and 0.992. The regression equation was established between the sensory scores and the chemical components Y=-56.39-4.37X1+12.04X2+12.22X4+5.2283X5+20.09X6-232.88X10,R2 was 0.9999.(3) Researches has been carried out on the different varieties and different seasons, different tender of fresh tea leaf materials to study the yellow tea tea quality, the results showed that the quality of different varieties, different seasons, different tenderness have a obvious difference. Six varieties of yellow tea water leaching and changes in the scope of 39.16%-45.58%; tea polyphenols variation range 21.80%-27.18%; free amino acid changes in the scope of 3.68%-4.80%; caffeine varies 3.83%-4.42%; soluble sugar range 3.75%-4.83%; theaflavins range 0.10%-0.16%; total leaf green element change range 0.09%-0.14%. Different varieties of sensory score results was Mengshan 9> Fuding Dabai> Sichuan tea group> chuannonghuangyazao> Zhu Yeqi> Fuyun 4; different seasons sensory score results was spring> autumn> summer. The results of different tenderness sensory score: single bud> one bud with a leaf> one bud with two leaves> one bud with three leaves.(4) Researches has been carried out on the different storage conditions about tea sensory, biochemical changes and component analysis, the results showed that the storage at room temperature for 6 months occurred significantly change the sensory quality of tea, tea quality characteristics to change by Green Tea yellow tea quality characteristics. Tea polyphenol oxidase activity showed a wavy descending trend. The main chemical components showed a obvious changes.Total amino acids content showed a big difference, 22 kinds of amino acids which were detected, including 7 kinds of essential amino acids, 5 kinds of non protein amino acids.5 kinds of amino acids in sweet storage Huangya (1.98mg/g)> Shihua (1.61mg/g)>processing Huangya (1.45mg/g), which increased Huangya the content of sweet. Catechin components existed significant differences, storage caused configuration change from "ester epicatechin" to "catechins". The content of the ester type catechins, EGCG and ECG, storage reduced 13.03% and 6.19%, and simple catechins contents of GCG and CG content was slightly increased, thus reduce the bitter taste of tea, taste turn and alcohol. Shihua, storage Huangya and processing Huangya were detected aroma group respectively 70,82 and 81, with low molecular weight alcohols, aldehydes and ketones in high, respectively,28,32 and 31. Storage caused linalool transformed most, while methoxy phenyl compounds deposited in the yellow tea was not detected. Present the sweet substance such as beta-ionone, dihydro Actinidia lactone, phenylethyl alcohol, beta ionone, thujopsis dolabrata pinene, beta-cedrene, increased significantly,1-glyceraldehyde, benzyl alcohol, decanal, geraniol, 2,6 dimethyl-5-2-heptenal, alpha muurolene, conducted to storage Huangya unique sweet aroma formation. |
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